1. Field of the Invention
The present invention relates to a DC switchgear and, more particularly, to a DC switchgear provided with a commutation-type DC circuit breaker.
2. Description of Related Art
The DC switchgear according to the present invention has a commutation-type DC circuit breaker.
Devices constituting a DC switchgear including a commutation-type DC circuit breaker are all disposed in a single common accommodating box in which the DC switchgear is accommodated. Japanese Patent Application Laid-open Publication No. 2000-50431 discloses an exemplary structure of a DC switchgear in which various types of devices are accommodated in an accommodating box.
For the DC switchgear disclosed in the Japanese Patent Application Laid-open Publication No. 2000-50431, for example, the devices disclosed as being accommodated in a single common accommodating box include a main switch, disposed at the bottom of the front inside the common accommodating box, which can be brought into and taken out of it, a non-linear resistor disposed behind the main switch, a commutating capacitor disposed above the non-linear resistor, control devices disposed in front of the commutating capacitor to control and operate various types of devices, a bus bar and connection conductors disposed in the internal space of the accommodating box, and an overcurrent detection relay attached to the bus bar.
The commutation-type DC circuit breaker having the above components is structured so that when an excessive current flows in a main circuit having the main switch and the like, a commutating switch is turned on after the main switch opens so as to supply a high-frequency AC current, that is, oscillating commutation current, involved in a discharge from the commutating capacitor. Therefore, the oscillating commutation current is superimposed on a main circuit current flowing in the main circuit and thereby a current zero is generated shutting off the excessive main circuit current.
In addition to the commutation-type DC circuit breaker, which opens and closes the main circuit, the DC switchgear has, in the common accommodating box, a disconnector for disconnecting the main circuit, a current transformer and voltage transformer for measuring and controlling electric power supplied to an external load, a protective relay for protecting the circuit, an auxiliary relay and switches for controlling the switchgear, and lamps and a failure indicator for indicating the status of the circuit breaker, a failure status, and the like.
As described above, conventional DC switchgears are structured in such a way that their all constituting devices are accommodated in a single common accommodating box.
However, the types, structures, and placements of the devices that constitute a DC switchgear and are accommodated on a per-switchgear basis vary depending on the application, specifications, and the like of the DC switchgear.
Patent Document 1: Japanese Patent Application Laid-open Publication No. 2000-50431